The oxidation of saturated hydrocarbons e.g. alkanes, particularly cycloalkanes, with active oxygen such as molecular oxygen or air to produce the corresponding alcohol, ketone and/or acid reaction product(s), has been an area of research activity for many years in view of the utility and environmental benefits of the reaction to the chemical industry.
The oxidation of cycloalkanes in particular has proved to be a difficult reaction to carry out, typically requiring harsh reaction conditions and/or resulting in poor conversion of the starting material and/or poor selectivities of desired reaction products. For example, it is know from the literature to oxidise an alkane such as cyclohexane, with air, in the presence of a cobalt catalyst. The reaction however requires conditions of high temperature and pressure to activate oxygen. Further, under these conditions, in order to obtain a reasonable selectivity of the products, the conversion or transformation rate of the starting material has to be suppressed below about 10%. An alternative reaction involves carrying out the autoxidation of a macrocyclic alkane e.g. cyclododecane, with molecular oxygen in the presence of a stoichiometric amount of boric acid, metaboric acid or boric anhydride to produce alkyl borate reaction products. These reaction products are hydrolysed in a later step, to provide the corresponding alcohol and boric acid. The conversion of the macrocyclic alkane starting material is still however generally poor, and therefore the overall yields of the desired reaction products are typically low.
A further catalytic system has been described in EP-A-824,962. This document describes a catalytic oxidation system comprising an N-hydroxyphthalimide compound of formula (1) below and a co-catalyst, which system is described as promoting the efficient oxidation of a substrate under relatively mild conditions. For example, the oxidation of cyclohexane using N-hydroxyphthalimide and a manganese (II) co-catalyst is described as proceeding at atmospheric pressure (1 atm) and a temperature of 100° C. to produce a carboxylic acid, with no formation of ketone and alcohol intermediates being observed. 
A further reported reaction was the oxidation of cyclododecane in the presence of N-hydroxyphthalimide, a cobalt (II) co-catalyst and oxygen at atmospheric pressure and a reaction temperature of 100° C.
Although the catalytic oxidation system proposed in EP-A-824,962 goes some way to enabling the catalytic oxidation reaction of alkanes, particularly cycloalkanes, to be carried out under comparatively mild to moderate conditions compared with earlier reported methods, there is still a need for new catalysts which demonstrate improved reactivity, being effective at conditions of even lower temperature compared with the catalysts of the prior art.
Additionally, or alternatively, typically the new catalysts will demonstrate improved selectivities and/or product conversion against known catalysts.